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FETAL DIAGNOSES & TREATMENT
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Parents expecting twins find
hope at Texas Children's |
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Although
twin-twin transfusion
syndrome is rare, physicians at Texas Children's treat two or three pregnant women each week — 70 percent of whom live outside the Houston area.
-Chron.com
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Read more
about Twin-Twin Transfusion Syndrome |
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| Texas
Children's Fetal Center specialists diagnose and treat
twin-twin transfusion syndrome. Members of the team include
(from the left) Tom Cunningham, R.N., Dr. Anthony Johnson,
Teresa Bagley, R.N., Dr. Kenneth Moise, Anita Hadley, R.N.,
and Karen Moise, R.N. |
Overview
Treatments:
Most pregnancies result in one baby. In about
one in 80 pregnancies, twins are conceived.
This can occur in one of two ways:
The more common way (which accounts for
two-thirds of
cases) is for the two different sperm to
fertilize two different eggs, resulting in what
is called a dizygotic (DZ) twin gestation.
These twins are often called fraternal twins.
In this type of twinning each twin has its own
sac of amniotic fluid and its own placenta
(afterbirth). Dizygotic twins have two sets of
membranes surrounding their amniotic fluid
sacs (one inner amnion layer and one outer
chorion layer), and therefore they are known as diamniotic, dichorionic.
In about one-third of twin pregnancies, one
sperm fertilizes one egg, but this splits into
two embryos resulting in what is known as
monozygotic (MZ) twins. These twins are often
referred to as identical twins since they have
the same genetic material. Approximately one-third
of MZ twins look just like fraternal twins on
prenatal ultrasound since there are two
separate amniotic sacs and two separate
placentas. However, in two-thirds of identical
twins, each twin has its own amniotic sac but
shares a common placenta. This type
of MZ twinning is called monochorionic,
diamniotic since there is an inner layer
surrounding the amniotic sac of each twin, but
there is only one common outer layer (chorion)
surrounding both of the sacs. This type of
twinning occurs in approximately one in 360
pregnancies. Monochorionic twins are at higher
risk for complications since they share a
common placenta.
Less than 1 percent of identical twins (about
one in 2,400 pregnancies) will have one
amniotic sac and one placenta for both twins.
This type of twinning is referred to as
monchorionic,
monoamniotic twinning. These twins are at very
high risk for loss of the pregnancy due to
entangled umbilical cords.
This condition
occurs only in those identical twins that are
monochorionic, diamniotic (one-third of all
identical or monozygotic twins). In almost all
of these pregnancies, the single
placenta contains blood vessel connections
between the twins. For reasons that are not
clear, in 15 percent to 20 percent of monochorionic,
diamniotic twins, the blood flow through these
blood vessel connections becomes unbalanced,
resulting in a condition known as twin-twin
transfusion syndrome (TTTS). This is not an
inherited or genetic condition. It is not
caused by something that a mother or father
has done or not done.
In TTTS, the smaller twin (often called the
donor twin) does not get enough blood while
the larger twin (often called the recipient
twin) becomes overloaded with too much blood.
In an attempt to reduce its blood volume, the
recipient twin will increase the urine it
makes. This will eventually result in the twin
having a very large bladder on ultrasound, as
well as too much amniotic fluid around this
twin. This is known as polyhydramnios.
At the
same time, the donor twin will produce less
than the usual amount of urine. The amniotic
fluid around the donor twin will become very
low or absent. This is known as oligohydramnios.
As the disease progresses,
the donor will produce so little urine that
its bladder may not be seen on ultrasound. The
twin will become wrapped by its amniotic
membrane (known as a “stuck” twin). Often the polyhydramnios of the recipient twin is the
first thing noticed by the patient due a
sudden increase in the size of the uterus.
Clothes may become tight fitting over a short
period of time. At other times the differences
in the amniotic fluid volumes between the
twins is only noted at the time of a routine
ultrasound.
Illustration:
Anastomosis
The diagnosis of TTTS is made with an
ultrasound evaluation that shows a twin pregnancy
with one placenta, twins of the same sex in
separate amniotic sacs, and polyhydramnios in
the recipient’s sac and oligohydramnios in the
donor’s sac. Amniotic fluid volume is measured
with ultrasound by determining the deepest
pocket measurement from the patient’s skin to
her back. This measurement is known as the
maximum vertical pocket (MVP).
Quintero1
has proposed five stages of TTTS based on
ultrasound findings:
Stage I: This is the initial way that TTTS
is seen on ultrasound. In stage I, there is
oligohydramnios in the donor’s sac with an MVP
of two centimeters or less (three-quarters of
an inch) and polyhydramnios in the recipient’s
sac with a maximum vertical pocket of fluid of
eight centimeters or more (just over three
inches). The bladder of the donor baby is
still seen.
Stage II: As defined above, there is
polyhydramnios and oligohydramnios, but the
bladder is no longer seen in the donor twin
during the ultrasound evaluation.
Stage III: Blood flow in the fetus can be
measured with a special type of ultrasound
called Doppler. In addition to the findings of
Stages I and II, careful study of the blood
flow in the umbilical cord and fetal ductus
venosus (the large blood vessel in the fetus
that returns blood to the heart from the
placenta) reveals abnormal patterns in Stage
III. These patterns can occur in either or
both fetuses.
In the umbilical cord, the diastolic flow can
be either absent or reversed in the umbilical
artery. This pattern is usually seen in the
donor twin. In the ductus venosus, the
diastolic flow can either be absent or
reversed. This pattern is usually see in the
recipient twin due to early heart failure. The
recipient twin can also exhibit leakage across
the main valve on the right side of the heart
– this is known as tricuspid regurgitation.
Stage IV: One or both babies shows signs
of hydrops. This means there is excess fluid
in parts of the baby such as swelling of the
skin around the head (scalp edema), fluid in
the abdomen (ascites), fluid around the lungs
(pleural effusions) or fluid around the heart
(pericardial effusion). These findings are
evidence of heart failure and are typically
seen in the recipient twin.
Stage V: One or both babies have died.
The survival of the twins is poorer when there
is progression to a higher stage over time. It
has been estimated that half of patients will
progress to a higher stage, 30 percent will
remain at the same stage and 20 percent will
improve to a lower stage.2, 3
An usual form of TTTS occurs in about one in
15,000 pregnancies. In these monochorionic
twins, one twin develops normally while the
other twin fails to develop a heart as well as
other body structures. The abnormal twin is
called an acardiac twin. In these
pregnancies, the umbilical cord from the
acardiac twin branches directly from the
umbilical cord of the normal twin. Blood flow
to the acardiac twin comes from the normal
twin, which is also known as a pump twin. This
blood flow is reversed from the normal
direction leading to the name for this
condition: twin reversed arterial perfusion
syndrome or TRAP. In some cases the blood flow
from the pump twin to the acardiac twin stops
on its own and the acardiac twin stops
growing. In other cases, the flow continues
and the acardiac twin continues to increase in
size. This eventually leads to heart failure
and polyhydramnios in the pump twin. Without
treatment, more than 50 percent of cases of
TRAP will result in the death of the pump
twin.
There are a number of ways to treat TTTS, any
of which many be the correct method depending
on ultrasound findings, the gestational age of
the pregnancy and a couple’s specific needs.
Left untreated, TTTS prior to 24 weeks’
gestation (six months of pregnancy), 80
percent to 90
percent of cases are associated with the loss
of one or both twins. If one of the twins
should die, the blood vessel connections in
the placenta can place the surviving twin at
risk for long-term brain damage in as many as
one-third of cases. In general, more advanced
stages of TTTS have a worse prognosis than the
earlier stages. When severe TTTS occurs at a
very early gestational age (prior to sixteen
weeks or the fourth month of pregnancy), the
option of termination of the pregnancy can be
considered due to the grim prognosis.
The various therapies that are available
target either the unequal fluid between the
twins’ sacs or interrupt the blood vessel
communications between the twins on the single
placenta. The successful outcome of these
treatments has been based on the number of
babies that survive, as well as the number of
babies who do not have brain damage. The
treatments that are currently available are
described below:
Reduction
amniocentesis
Serial amniocentesis involves the removal of
the excessive amniotic fluid from the sac of
the recipient twin using a needle that is
passed through the maternal abdomen.
The amount of amniotic fluid removed will
vary based on the initial volume in the
recipient sac, the gestational age and the
development of uterine contractions during the
procedure. As a general rule no more than
three liters (approximately two and one-half
quarts) of amniotic fluid is removed at any
one time. The procedure is usually completed
within 30 minutes or less. The procedure may
temporarily restore the balance in the
amniotic fluid in both twins’ sacs. This
technique may be useful for milder cases of TTTS that occur later in pregnancy.
However, reduction amniocentesis usually
requires repeat procedures to be undertaken
every few days to weekly when the fluid
returns to high levels. The procedure is
generally not thought to be effective for more
advanced stages of TTTS (Stages III and IV).
Complications of repeated amniocenteses for
the treatment of TTTS include premature labor
with early delivery in 3 percent of cases,
premature rupture of the membranes in 6
percent of cases, infection in about 1 percent
of cases, and premature separation of the
placenta from the wall of the womb (called an
abruption) in 1 percent of cases.4
Pregnancies managed with serial
reduction amniocentesis on average deliver by
29 to 30 weeks of gestation (approximately ten
weeks prior to the “due date”).4, 5
If there is progression of TTTS to a more
advanced stage, serial amniocenteses will
reduce the success rate for such procedures
such as laser (see below). Reported survival
rates have varied from 18 to 83 percent,
with a recent study noting that just over half
(56 percent) of severe TTTS cases managed with
reduction amniocentesis will end with at least
one infant without brain damage.5
Approximately, 20 percent to 25 percent of the TTTS
survivors from pregnancies treated with
reduction amniocentesis have been found to
have long-term developmental delay.
Illustration:
Reduction
Amniocentesis
Septostomy (also known
as microseptostomy)
Septostomy
is the creation of a hole in the membrane
between the babies’ sacs using a needle. This
causes fluid to move from the amniotic sac
with excessive fluid (the recipient’s sac)
into the sac with absent or low fluid (donor’s
sac). Since septostomy is performed with a
needle that is used to perform amniocentesis,
complications of infection, premature labor
and premature rupture of the membranes are
rare. Septostomy carries the additional
potential risk for the hole to become larger
between the two sacs and could even allow the
babies to share the same amniotic space if the
entire separating membrane becomes disrupted.
This has been reported to occur in 3 percent
of septostomies.6 In the worst case
scenario, the umbilical cords of the twins
could become entangled, leading to the death of
one or both fetuses. In one large series,
survival to birth was 80 percent for at least
one twin and was 60 percent for both twins.6
Patients undergoing septostomy typically
require fewer procedures than those treated
with amnioreduction. There is no data
currently available regarding neurologic
outcome in survivors of septostomy.
Illustration:
Septostomy (also known as Microseptostomy)
Selective laser
ablation of the placental anastomotic vessels
In more advanced stages of TTTS (Stage II and
higher) laser ablation of the communicating
vessels on the placenta between the twin
fetuses can be a curative procedure.
The procedure is performed in an operating
room. After the patient’s abdomen has been
washed with an antiseptic and covered with
sterile paper drapes, an ultrasound is
performed to determine the appropriate spot to
enter the uterus. The skin is then injected with
an anesthetic medication to “numb” the area
and deep tissues directly under the selected
site. An anesthesiologist will also administer
medications through an intravenous line to
produce sedation. A small skin cut is made to
allow the introduction of a thin hollow tube
and needle. The instruments are inserted under
ultrasound guidance into the amniotic sac of
the recipient twin. The needle is removed and
a telescope (fetoscope) with a thin fiber to
carry the laser energy is then inserted
through the hollow tube. The fetoscope is used
to look directly at the blood vessels on the
surface of the placenta. Vessels that are
found to communicate between the twins are
then closed using laser light energy. At the
completion of the surgery, the extra amniotic
fluid in the recipient twin’s sac is removed
to achieve a normal volume. The procedure may
take 45 minutes to two hours depending on
the difficulty of the case.
Because the fetoscope requires a larger hole
to be made into the amniotic cavity than would
be the case with an amnioreduction or
septostomy procedure, laser ablation is
associated with a higher risk of complications
such as premature contractions, premature
rupture of the membranes (15 percent to 20 percent of
cases), placental separation (2 percent) and
infection. For this reason, special
medications to prevent contractions and
antibiotics to prevent infection will be given
before and after the procedure. In addition,
laser therapy may be associated with unique
risks since the laser energy may cause certain
areas of the placenta or blood vessels on the
surface of the placenta to bleed.
Laser ablation has been shown to result in the
survival of at least one twin in 70 percent to 80
percent of cases and both twins in one-third of
cases.5, 7, 8 Should one fetus die
after the procedure, the likelihood that the
surviving fetus will develop complications is
reduced from 35 percent to approximately 7
percent. This is because the babies are no
longer sharing blood vessels between them. In
one-third of cases, neither twin will survive.
Studies to date have indicated that
approximately 8 percent of survivors following
laser ablation will have a long-term mental
handicap. This is approximately half of the
rate of problems seen in survivors treated
with amnioreduction.5
Illustration:
Laser Ablation of the placental anastomotic
vessels
Selective cord coagulation
In some cases, a couple may make the difficult
decision to proceed with the purposeful loss
of one twin to save the other twin. This
procedure is used when laser ablation of the
connecting vessels is not possible or if one
of the twins is so close to death that laser
ablation would likely not be successful. By
stopping the flow in the cord of the dying
twin, the other twin can be protected from the
consequences of its sibling’s death. The
procedure is performed through the use of a
special forceps that is placed into the
amniotic sac of the recipient twin while
watching with ultrasound. The umbilical cord
is then grasped and electrical current is
applied to burn (coagulate) the blood vessels
in the cord so that the blood flow will stop
to this fetus. The communication between the
fetuses is definitively ended; however, this
eliminates the chance of survival for one of
the twins. Complications of this procedure
include premature delivery and premature
rupture of the membranes. Rupture of the
membranes has been reported to occur in about
20 percent of cases. Survival of the one
remaining fetus can be expected in 85 percent
of cases.
Illustration:
Selective
cord coagulation
This procedure is usually reserved for TRAP
sequence. The umbilical cord of the acardiac
fetus is usually very short and difficult to
see on ultrasound. As a result, it is often
difficult to stop the blood flow into the acardiac fetus by coagulation of the umbilical
cord. For this reason, a major blood vessel in
the acardiac fetus is often targeted as the
site for occlusion of blood flow. This can be
accomplished through the use of a
radio-frequency ablation catheter. In this
procedure, a specialized needle is passed into
the amniotic fluid and then into the body of
the acardiac fetus. A special current is then
applied to the needle to burn the area around
the major blood vessel in the abnormal fetus.
This will stop the blood flow and allow the
pump twin (normal twin) to no longer have to
send blood to the acardiac twin. Complications
of infection, premature contractions and
premature rupture of the membranes can occur
as in any needle procedure. In one series, the
risk for premature rupture of the membranes
was 8 percent.9 In this same
series, the chance for a successful live birth
for the pump twin was 90 percent.
Illustration: Radiofrequency Ablation
You
will be scheduled for an ultrasound evaluation
with one of our maternal-fetal medicine
specialists at Baylor College of Medicine's
Baylor Clinic. The physician will discuss all
findings and will review the treatment
options, surgical procedures, prognosis, and
recommended follow-up care. We will be able to
answer your questions and concerns at this
time.
Next, you will meet with or have a phone
conversation with our fetal therapy
coordinator who will be able to answer any
further questions that you and your partner
may have. In addition, the fetal therapy
coordinator will assist you with any special
needs, including overnight accommodations. You
will receive a folder that contains
information you will need for surgery and
additional information that you will find
helpful.
After your ultrasound and consultation, you
will have a pre-operative consultation with
an anesthesiologist, which will be held in
the labor and delivery unit of
St. Luke's Episcopal Hospital. You
will also have blood samples drawn at that
time. A surgery consent form will be given to
you to review. It explains the surgery in
terms you can understand. You will also be
given several consent forms for collection of
data for an ongoing study of research to help
us better understand the treatment of
twin-twin transfusion syndrome. You will then
be discharged home or back to your hotel room.
The night before surgery, you will not be
allowed to eat or drink for a defined amount
of time (usually six to eight hours). This is
to prevent the risk of vomiting during
surgery. In medical terms, this is known as "NPO"
(nothing by mouth). We will give you a time to
come to St. Luke's Episcopal Hospital on the day of surgery.
Your family may come with you, but will be
asked to wait for you in one of our labor or
waiting rooms during the surgery. An intravenous line
(IV) will be inserted by needle stick to give
you fluids and medications during surgery. An
ultrasound will be performed prior to going to
the operating room to confirm that both twins
are alive. One of the specially trained nurses
that will be assisting in surgery and an
anesthesiology resident will accompany you to
surgery.
You will be transported to the operating
room where you will be asked to move on to the
operating table. You will be covered with a
warm blanket and a pillow will be placed under
your knees to keep you comfortable during
surgery. You may be rolled to your left side
to keep your uterus from causing your blood
pressure to fall. A belt will be placed across
your legs to prevent you from sliding off the
operating room table. Your abdomen (belly)
will be cleaned with an iodine solution (let
your nurse know if you are allergic to
iodine). Then you will be covered with sterile
paper drapes. The top of the drapes will be
attached to a pole so that you do not need to
watch the procedure. Medication will be given
through your IV to relax you. Surgery is
performed under local anesthesia, meaning you
are awake but relaxed, and your abdomen is
numbed where the instrument is inserted. An
anesthesiologist will stay with you throughout
the procedure. You will be given additional
medication for discomfort as needed. On rare
occasions, general anesthesia, meaning you are
put to sleep, may be used. During surgery, one
or two small incisions approximately
one-tenth of an inch long will be made on the
abdomen. These incision(s) are small. You will
have short pieces of specialized tape (steri-strips)
placed on your skin to close this incision at
the end of the procedure.
Following surgery, you will be taken to the
recovery room in labor and delivery or a labor
room where you and your fetus or fetuses will be
closely monitored. Your abdomen will be
a little tender or sore once the local
anesthetic wears off. You may be given
medications after surgery to relax the uterus
and stop any contractions. The pain and
discomfort after surgery is usually minimal.
If needed, pain relief medicine is available.
Your spouse or other support person may
remain with you in your room. Following
surgery, you may have food as tolerated. You
will be admitted to the hospital for an
overnight stay. That night, activity is
restricted to bathroom privileges only, but
this depends upon your specific condition. You
will undergo an ultrasound the day after
surgery to determine how the babies are doing.
You will then be discharged home to the
care of your primary obstetrician and/or your
referring maternal-fetal medicine specialist.
Your instructions will include bed rest with
bathroom privileges for seven days after the
surgery, with a gradual increase in activity.
We will also ask that you get a thermometer
and take your temperature three times per day.
You should notify your primary obstetrician
for any increase above 100.4°F of an oral
temperature. The site of the surgery can get
wet in a shower within 24 hours of the
procedure. You can remove the steri-strips over
the incision yourself one week after the
surgery.
After four weeks you can resume
normal activity based on your pregnancy
condition and the comfort level of your
primary obstetrician. Weekly ultrasounds are
recommended for the next month. After that
time, if all is going well, ultrasounds are
performed as directed by your doctor.
Although
you are returning home, we will continue to
follow your pregnancy closely through our care
coordinator. Please make arrangements with
your doctor to forward your ultrasound reports
and any other pertinent information to us. We
also ask that you inform your obstetrician and
labor nurse that we would like to have your
placenta sent back to us after you delivery.
This information is useful to further our
knowledge and will assist in the future
treatment of patients with TTTS.
Social services and pastoral care are
available for all our patients and their
families. If you would like to see them at any
time, you need only to request it and they can
be contacted. We are sensitive to the
psychological, social and spiritual needs of
our families. We will provide any support that
is necessary. Please contact us if you have
any questions, concerns or special requests.
For our out of town patients, we realize that
traveling may be difficult or stressful and
want you to know that we will do everything we
can to accommodate your special needs and
schedule.
Back to Diagnoses
References
1. Quintero RA, Morales WJ, Allen MH, Bornick
PW, Johnson PK, Kruger M. Staging of twin-twin
transfusion syndrome. J Perinatol 1999;
19:550-5.
2. Taylor MJ, Govender L, Jolly M, Wee L, Fisk
NM. Validation of the Quintero staging system
for twin-twin transfusion syndrome. Obstet
Gynecol 2002; 100:1257-65.
3. Dickinson JE, Evans SF. The progression of
disease stage in twin-twin transfusion
syndrome. J Matern Fetal Neonatal Med 2004;
16:95-101.
4. Mari G, Roberts A, Detti L, et al.
Perinatal morbidity and mortality rates in
severe twin-twin transfusion syndrome: results
of the International Amnioreduction Registry.
Am J Obstet Gynecol 2001; 185:708-15.
5. Senat MV, Deprest J, Boulvain M, Paupe A,
Winer N, Ville Y. Endoscopic laser surgery
versus serial amnioreduction for severe
twin-to-twin transfusion syndrome. N Engl J
Med 2004; 351:136-44.
6. Moise KJ, Jr., Dorman K, Lamvu G, et al. A
randomized trial of amnioreduction versus
septostomy in the treatment of twin-twin
transfusion syndrome. Am J Obstet Gynecol
2005; 193:701-7.
7. Hecher K, Plath H, Bregenzer T, Hansmann M,
Hackeloer BJ. Endoscopic laser surgery versus
serial amniocenteses in the treatment of
severe twin-twin transfusion syndrome. Am J
Obstet Gynecol 1999; 180:717-24.
8. Quintero RA, Dickinson JE, Morales WJ, et
al. Stage-based treatment of twin-twin
transfusion syndrome. Am J Obstet Gynecol
2003; 188:1333-40.
9. Lee H, Wagner A, Bobert B, et al.
Radiofrequency ablation for TRAP sequence. Am
J Obstet Gynecol 2005; 191:S18.
 
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